1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a computer program product.
2. Description of the Related Art
In a conventional image forming apparatus that analyzes PDL and performs drawing, there is an image processing technology for converting a color image into an image expressed by few color values in order to perform the drawing in an image format output from a printer engine. The image processing is performed by developing an image having RGB values on a memory by using a drawing command obtained by analyzing PDL, performing a color conversion, a gradation process, and the like, and outputting the result to the printer engine.
When drawing an image on a memory, drawing requires time because a process for clearing a background, a logical operation process, a semi-transparent process, and the like are performed by RGB values. Japanese Patent Application Laid-open No. H6-139364 discloses a technology for developing input image data on a color palette and performing drawing by using the color palette. Moreover, Japanese Patent Application Laid-open No. H11-78126 discloses a technology for performing a subtractive color when the number of color palettes exceeds a predetermined number.
Furthermore, Japanese Patent Application Laid-open No. 2007-216675 discloses a technology for modifying the number of bits indicative of the number of palettes of a color palette every image data.
In Japanese Patent Application Laid-open No. H11-78126, because the number of colors of image data is reduced in accordance with the number of color palettes, this technology cannot correspond to the output of an image that requires high picture quality. Moreover, in Japanese Patent Application Laid-open No. 2007-216675, because the number of colors of a color palette increases when the number of color values of input image data increases, the speed of a drawing process decreases.